The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An aircraft is moved by several turbojet engines each housed in a nacelle also accommodating a set of auxiliary actuating devices relating to its operation and ensuring various functions when the turbojet engine is in operation or shut-down.
In particular, these auxiliary actuating devices comprise a mechanical thrust reverser system and a variable nozzle system.
The role of a thrust reverser, during the landing of an aircraft, is to improve the braking capability of the latter by redirecting forwards at least one portion of the thrust generated by the turbojet engine. In this phase, the thrust reverser allows directing forwardly of the nacelle all or part of the gas flows ejected by the turbojet engine, thereby generating a counter-thrust which is added to the braking of the wheels of the aircraft. For this purpose, a thrust reverser comprises on either side of the nacelle a movable cowl displaceable between, on the one hand, a deployed position which opens a passage in the nacelle intended for the diverted flow during the braking phase, and on the other hand, a stowed position which closes this passage during the normal operation of the turbojet engine or when the aircraft is at stop.
The movable cowls may fill a diverting function or simply activate other diverting means.
In the case of a cascade-type thrust reverser, the reorientation of the air flow is performed by cascade vanes, associated to reversal flaps which block a portion of the air circulation flow path, the cowl having a simple sliding function aiming at uncovering or recovering these cascade vanes.
Moreover, besides its thrust reversal function, the sliding cowl belongs to the rear section and presents a downstream side forming the ejection nozzle aiming at channeling the ejection of the air flows. In the case of a cascade-type thrust reverser, the sliding cowls are moved by actuators synchronized with each other and equipped with locks for retaining in the closed position in flight. In the case of such a hydraulically-controlled thrust reverser, the hydraulic actuators integrate inner screws which turn with the translation of their hydraulic rod. The rods are blocked in rotation by clevises for linkage to the movable cowl, thus the displacement is performed by a mere translation of the cylinder rods. A transmission and linking device by multiple wound-web flexible cables links the screws of the actuators to each other at the level of the fixed structure. Thus, the translational movement of the actuators is synchronized, consideration being made of the stiffness of the flexible cables which servo-control a homogeneous rotation of the screws. The optimum section of the ejection nozzle may be adapted depending on the different flight phases, namely the take-off, climb, cruise and descent phases.
It should be noted that the operating phases of the variable nozzle and of the thrust reverser are distinct from each other, the variable nozzle being inactivated when the thrust reverser is activated at landing.
Among the different embodiments of ejection nozzles known in the prior art, it is known in particular to perform the variation of the outlet section of the nozzle using one or several movable element(s), such as pivoting flaps.
In order to actuate the adaptive nozzle independently of the thrust reversal means, in particular during take-off, each movable portion (thrust reverser cowl/nozzle flaps) is moved by a set of actuators distinct for these two movements. This is in particular the case of the actuation system described in the document GB 2 449 281, in which the actuation of the nozzle is performed by an actuator having a telescopic rod displaceable in translation via a nut-and-screw system and whose screw is driven in rotation by a motor secured to a fixed portion of the nacelle, the thrust reverser cowl being, in turn, driven in translation by a set of independent actuators. A drawback of this embodiment is that there are duplicated activation control means between the movement of the thrust reverser and the movement of the nozzle actuation. In addition, the supply of energy and measurements of the cowl or of the variable nozzle flaps is made difficult because it is conveyed throughout the thrust reverser cowl, which, in turn, should be displaced at landing.
In order to reduce the weight of the nacelle, it has been proposed to use one single actuator comprising appropriate means for locking/unlocking the adaptive nozzle on the sliding thrust reverser cowl, thereby enabling a sequenced displacement of the thrust reverser cowl and of the nozzle, with one single actuator.
The document GB 2 446 441 describes such a control architecture for actuating both a thrust reverser device associated to a variable nozzle device, and provides for this purpose an actuator comprising two concentric pistons movable in translation, the first piston being connected to the thrust reverser cowl, and the second piston being linked to the nozzle, each piston being hydraulically controlled independently of each other.
This solution appears to be particularly complex to carry out. In addition, in this double-translation solution, guiding two movable elements poses issues in taking up the radial degrees of freedom because of the relative clearance between the thrust reverser cowl and its guide rails and because of aerodynamic deformations.